PEOPLING × GENETICS

The Expansion That Peopled the World

~70,000–50,000 years ago

Palaeolithic · Middle Stone Age · Last glacial

Nearly every genome outside Africa descends from a single expansion of foragers that left the continent between about 70,000 and 50,000 years ago. On the way, these people met Neanderthals and had children with them. The mixing happened once, around 49,000 to 45,000 years ago, and left about two per cent of Neanderthal DNA in all their descendants, which is how we can tell they still formed a single connected population at that date. Over the following twenty thousand years, the expansion became worldwide.

Why it matters

This is the fork from which most non-African ancestry branches: Europeans, Asians, Australians and Native Americans trace the bulk of their descent to the same expansion, and carry much the same share of Neanderthal DNA to prove it. The rest of the story stays African: our species had already lived there for a quarter of a million years, in populations that no single birthplace can summarise.

Dating & uncertainty

People had left Africa before: fossils place our species in the Levant around 180,000 years ago, and again between about 120,000 and 90,000 years ago. Those excursions left no major trace in living genomes. The interval here, roughly 70,000 to 50,000 years ago, dates the one expansion that today's non-African ancestry descends from; genetic clocks narrow its later stages but not its first step.

Sources

1. Hallast et al. (2020), Human Genetics · A Southeast Asian origin for present-day non-African human Y chromosomesdoi:10.1007/s00439-020-02204-9
2. Sümer et al. (2024), Nature · Earliest modern human genomes constrain timing of Neanderthal admixturedoi:10.1038/s41586-024-08420-x
3. Bergström et al. (2021), Nature · Origins of modern human ancestrydoi:10.1038/s41586-021-03244-5
4. Stringer & Galway-Witham (2018), Science · When did modern humans leave Africa?doi:10.1126/science.aas8954

Our species’ history as one day

18:40:005 h 20 min before midnight

if the 315,000 years of Homo sapiens were compressed into a single day